Grinding apparatus



Feb. 19, 1957 c. GARRISON GRINDING APPARATUS 3 Sheets-Sheet 2 Filed Oct.24, 1951 I INVENTOR I ['LJPPUJFD L. FARR/ISBN ATTO R N E C. L. GARRISONGRINDING APPARATUS Feb. 19, 1957 3 Sheets-Sheet 3 Filed 001;. 24,. 1951INVENTORZ CLIFF 0RD L. EARRISUN.

ATTORNE United States Patent GRINDING APPARATUS Clifford L. Garrison,Adrian, Mich., assignor to 0li'ver Instrument Company, Adrian, Mich., acorporation of Michigan Application October 24, 1951, Serial No. 252,855

2 Claims. (Cl. 51-100) This invention relates to a method of grindingand apparatus for carrying out the method, the invention relating moreespecially to a method of grinding tool bits or similar articles whereinthe grinding or abrasive effectiveness is improved over prior methodsand apparatus.

It has been conventional practice to configurate and resharpen form toolbits through the utilization of a tool holder provided with a templatemeans for guiding the tool bit during grinding operations and to limitor tenninate the grinding operation upon the form or shape of thetemplate being reproduced upon the tool bit. In such devices and methodswhich have been utilized for this purpose, the peripheral surface of acylindrical grinding wheel or the flat uniplanar surface of a cup-shapedwheel has been used in conjunction with a uniplanar surface orstraightedge cooperating with a template which serves as a guide meansto enable an operator to grind the tool bit to the templateconfiguration.

In many form tool bits there are uniplanar zones'or wall portionspresented to the wheel during grinding operations which are of extensivearea. The presentation of a large area of the form tool bit or elementto the grinding wheel slows up the grinding operation materially andadditionally causes excessive heating of both the grinding wheel and thework. The retardation in the grinding effectiveness appears to be due tothe engagement of a large area of surface with the wheel, and in mostinstances the effectiveness of grinding is reduced as the area of theelement presented to the wheel is increased. Furthermore, the less thegrinding effectiveness, the more is the heat that is generated throughthe frictional contact of the work with the wheel, usually accompaniedby an increased tendency for the wheel surface to become glazed and tooverheat the work. When tool bits formed of very hard alloys such astungsten carbide are ground by the above-mentioned methods, the toolbits when subjected to any appreciable heating during grinding arereadily susceptible of cracking and fracturing. Hence, such priormethods as a practical matter have been unsatisfactory for forming andsharpening hardened form tool bits.

The present invention embraces a grinding apparatus wherein duringgrinding operations the area of the work presented to the grinding wheelis restricted substantially to a line contact between the work' and thewheel.

An object of the invention is the provision of an apparatus for carryingon grinding operations wherein a minimum area of abrasive engagement isestablished between the work and the grinding wheel whereby the speed ofgrinding is increased with a minimum of friction and heat developed byreason of the contact between the work and the grinding wheel. An'otherobject of the invention is the provision of apparatus utilizing agrinding wheel having a transverse,

arcuately-shaped, peripheral grinding zone adapted for cooperation witha tool holder and template means whereby articles having uniplanar orconvex surfaces maybe formed or sharpened by engagement of the work withthe transversely curved zone of the wheel in a manner wherein a minimumarea of the work is at all times presented to the grinding wheel wherebythe speed of grinding is greatly increased over prior grinding methods.

Another object of the invention is the provision of apparatus forpresenting work to a grinding wheel in a manner at all timesestablishing a substantially linear or narrow width of contact orabrasive area between the work and the wheel, the arrangementfunctioning in conjunction with template means for imparting variousconfigurations or shapes to the work.

A further object of the invention is the provision of an apparatus forpresenting a form tool bit or the like to a grinding wheel in a mannerwhereby grinding operations may be distributed over a substantial areaof the grinding wheel to eliminate rapid wear of the wheel in aparticular zone, the manner of engagement of the work with the wheelbeing confined at all times to a narrow linear area.

Another object of the invention resides in the provision of an apparatusfor grinding wherein the abrasive zone of the grinding wheel iscontoured to an arcuate configuration with which is associated a toolholder, template-follower and guide arrangement to effect asubstantially linear engagement of a tool being ground with the grindingwheel.

A further object of the invention resides in an apparatus including agrinding wheel having an arcuately contoured peripheral surface adaptedfor cooperation with a template and follower means cooperativelyassociated with a grinding machine and a support for elements to beground whereby rectilinear surfaces and convex surfaces of the items tobe ground may be effectively shaped through engagement with the grindingwheel peripheries without at any time during the grinding operatinginvolving any but a narrow linear engagement with the grinding wheel.

Further objects and advantages are within the scope of this inventionsuch as relate to the arrangement, operation and function of the relatedelements of the structure, to various details of construction and tocombinations of parts, elements per se, and to economics of manufactureand numerous other features as will be apparent from a consideration ofthe specification and drawing of a form of the invention, which may bepreferred, in which:

Figure 1 is a front elevational view of a grinding machine adaptable forcarrying out the method of grinding of the invention;

Figure 2 is a fragmentary side elevational view of a portion of themachine shown in Figure 1;

Figure 3 is an elevational view of a tool bit holder illustrating therelative positions of the template and guide means and engagement of atool bit with a grinding wheel during a grinding operation;

Figure 4 is a top plan view of the construction illustrated in Figure 3;I

Figure 5 is an enlarged sectional view through the peripheral zone of agrinding wheel illustrating the character of engagement of the work withthe grinding wheel;

Figure 6 is an end elevational view of the construction illustrated inFigure 4;

Figure 7 is an elevational view of an apparatus for truing a grindingwheel for carrying out the grinding method of the invention;

Figure 8 is a plan view of the guide and follower construction for thewheel-truing mechanism illustrated in Figure 7;

Figure 9 is a top plan view of a follower bar forming a part of thewheel-truing apparatus;

Figure is an elevational view of the guide bar showing the specificcontour of the guide engaging portion of the bar;

Figure 11 is a sectional view taken on the line 11-41 of Figure 10, and

Figure 12 is a diagrammatic view illustrating the I618: tive proportionsof the transverse curvature of the-grinding wheel periphery and thecurvature of the template guiding means.

While I have illustrated a machine especially adapted for carrying out anovel method of grinding or shaping tool bits, it is to be understoodthat'the principles of the invention may be utilized in grinding,shaping orabrading various kinds of tools or other work which may bereadily shaped or abraded by grinding methods.

Referring to the drawings in detail, the machine or apparatus isinclusive of a frame structure comprising a base or pedestal 12, anintermediate portion 14 which forms a fluid receptacle or basin tocollect the coolant fluid used during grinding operations, the portion14 supporting an upper frame element 16,,the components of the framebeingheld in assembled relation by bolts (not shown) or other suitablemeans. The base or pedestal 12 is formed interiorly with a reservoir 13adapted to contain a supply of coolant fluid which is circulated bymeans of a suitable fluid circulating pump 15 of conventional character.The pump is connected with a pipe 18 and a flexible hose or tube 19 forconveying the coolant fluid to the grinding surface or zone of thegrinding wheel and onto the tool bit or other work being ground, thecoolant fluid also serving to entrain and convey cuttings and abradedmaterial away from the grinding zone.

The intermediate portion 14 of the frame is formed to a troughconfiguration which is bounded at its periphery 21 with an upwardlyextending flange to collect the coolant fluid which is returned througha suitable passage to the reservoir in the base 12.

The upper frame element 16 supports a housing portion or enclosure 25within which is disposed a grinding wheel 27 mounted upon a shaft 28journalled in suitable bearings (not shown) carried by the frame element16. A pulley 30 is secured to one end of the shaft and is engaged by apower transmission belt 32 connected with a second pulley 33 driven by amotor 35 supported by the base portion 12. The pulley arrangement andbelt 32 are enclosed within a suitable sheet metal shroud 34.

The grinding wheel housing 25 has a downwardly extending portion 36which is bored to accommodate a shaft 37 whereby the housing 25 andelements carried thereby are pivotally supported for adjustment aboutthe axisof the shaft 37 relative to the grinding wheel for purposes tobe hereinafter explained. The housing 25 is made of separable sectionsso as to admit the assembly of the housing to enclose the grinding wheel27. Means is-provided for adjusting the housing 25 about the axis of,its supporting shaft 37. To this end, the housing 25 is provided with aboss 40 which is bored to accommodate a shaft 41 having a threadedportion passing through a nut 43 which is swivelly supported formovement about the axis of a supporting stub shaft 45. The shaft 45extends through a bore provided in a projection 47 integrally formedwith the frame 16. The shaft 41 is provided with a suitable hand wheel48, rotation of which causes the threaded portion of the shaft 41cooperating with the nut 43 to move or adjust the housing structure 25about the axis of the housing supporting shaft 37.

In carrying on grinding or abrading operations, the tool bit or elementto be resharpened or shapedto a predeterminedconflguration is preferablysupported upon a relatively movable member or tool holder disposed inpre? determined relation to the grinding Wheel. The arrangement includesadjusting means to grind tool bits or other work of various sizes andshapes as Well as to impart various clearance angularities thereto.Theforward portion of the housing structure 25 is provided withavergtically extending portion 50 provided with ways 51 upon which isslidably supported a member 52. The member 50 is provided with athreaded bushing 53 through which a threaded shaft 54 extends, the upperportion of the shaft journalled in a boss portion 56 secured to themember 52, a. hand wheel 58 being secured to the extremity of the shaft54. Rotation of the hand wheel 58 threads the shaft 54 relative to thethreaded bushing 53 carried by the portion 50 to cause rectilinearmovement of the member 52 along the Ways 51. The member 52 is providedwith a plurality of g'raduations 60arranged for cooperation with arelatively stationary index 61 formed on member 59 to facilitate theaccurate rectilinear positioning or adjustment of the member 52. Agrinding machine of this character is disclosed and described in U. S.patent to Edd C. Oliver, No. 2,552,645.

The member 52 is provided with means upon which a tool bit holder orsupporting member may be mounted during grinding operations. In theapparatus illustrated, the member 52 is formed with a forwardlyextending ledge 64 which carries a ball-shaped element or support 66 fora tool holder 68. The holder 68 is of the character illustrated inFigures 2, 3 and 6 and is adapted to carry or support a tool bit 70 orelement to be ground, the lower portion of the holder 68 beingconfigurated with a semispherical socket 71 adapted to snugly fit theball sup port 66 in a manner to be manually movable or oscillatablcabout the center of the spherical or ball-shaped support 66.

The upper extremity of the holder 68 is provided with a pad portion 74adapted to support a template 75 which may be securely held in place bymeans of a thumb screw 76 threaded into a bore in the upper end of theholder. The operative edge portion 73 of the template may be shaped orconfigurated to the contour to be ground or imparted by abrasion to thetool bit and is adapted for cooperation with a guide block or plate 80having iis forward face 81 of convex curvature for a purpose to behereinafter explained.

The tool bit or blank 70 is supported in the holder 68 in a mannerwhereby it may be quickly inserted and re moved. As illustratedparticularly in Figures 3 and 6, the bit 70 is mounted in a groovedblock 83 which is engaged by a cam locking member 85 pivoted upon a pin86, a manipulating screw 87 engaging cam member 85 to force the latterinto locking engagement with the block 83 to secure the tool bit in theholder.

One of the important features of the present invention is the provisionof a method whereby the entire operative or cuttingportion of a tool bitmay be rapidly fashioned. ground or abraded to the desired configurationof the pat tern or operative contour of the template 75. In theillustrated embodiment of the tool holder, the tool bit retainerv block83 is disposed so that the upper surface of the tool bit 70 is midwaybetween the center of the ball receiving socket 71 and the template 75.By this arrangement the template pattern may be made twice the size ofthe shape to be imparted to the nose of the tool bit thus providing fora high degree of accuracy of formation of the cutting or operativeportion of the tool bit.

The invention includes the feature of presenting the tool bit to thegrinding wheel in such a manner that during the reproduction of thetemplate configuration on the tool bit by the grinding operation, thezone of engagement of the tool bit with the grinding wheel is a narrowlinear area of contact. In this manner, grinding may be carried on at arapid rate with a minimum of friction developed because of the minimumzone of grinding. As a grinding operation progresses in imparting thedesired shape to the tool bit, the grinding area approaches a linecontact, a condition attained substantially at the time of completion ofthe grinding operation as determined by the template. Thus by reducingthe zone of actual abrasion to a minimum area, applicant has obtainedthe benefit of increased abrasive speed and at the same time reduced toa; minimum. the possibilities of overheating either the wheel or thetool by a reduction in the friction heat developed by grinding.

In a preferred apparatus, the peripheral zone of the wheel 27 upon whichgrinding operations are carried on is of a transverse convex curvatureas exemplified in Figures 4, and and 12, the arc of curvature of thewheel periphery being indicated at 90. It is imperative that there be anaccurate correspondence in curavture of the guide means for the tool bitholder and the transverse curvature of the grinding wheel in order thatthe shape of the template be accurately reproduced on the tool bit bygrinding. To attain this coordination, the abutment or guide 80 for thetemplate 75 has its forward face curved in a transverse direction as at81 of a radius twice that of the transverse curvature of the peripheralgrinding zone of the wheel 27. This relation is diagrammaticallyillustrated in Figure 12.

The illustration in Figure 5 of the drawings exemplifies the characterof engagement of the formed end portion of the tool bit 70 with thecurved grinding wheel face whereby a very narrow band or substantially aline engagement is established between the tool element being ground andthe grinding wheel. In Figure 5 the engagement of the template 75 withthe curved surface 81 of the template guide or abutment 80 issuperimposed to illustrate the character of engagement of the templatecontour with the curved guide. It will be apparent from the foregoingdescription that the operator manipulates the tool holder 68 in a mannerto oscillate the holder about the universal or ball support 66 so thatall of the nose portions or cutting zones of the tool bit are broughtinto grinding or abrading engagement with the grinding wheel face aspermitted by the contour of the template 75 en gaging the curved guide80 which serves. to limit the extent of grinding of the tool bit at anyone setting of the tool bit in the holder. By reason of the transverseconvex curvature of the grinding wheeland the mounting of the tool sothat all portions of the nose end thereof may be presented to the wheelby manipulation of the holder 68 about the center of the support 66, thegrinding area or engagement of the wheel with the tool does not exceed anarrow linear zone of contact which in practical operation provides aminimum area for effecting grinding operations. By providing for aminimum area of grinding, the cutting or abrading speed is greatlyincreased and the friction which ordinarily would be designated as wasteheat energy is reduced to a minimum. Hence, heating of the grindingwheel and the tool is also proportionately reduced and the grindingefliciency thereby improved.

The grinding apparatus of the invention is especially adaptable forgrinding extremely hard tools such as those fabricated of tungstencarbide, and they may be ground successfully through the use of thisapparatus because of the presentation of a minimum area thereof to thegrinding wheel. Applicants apparatus is usable to advantage in all formsof tool bit contour or configuration except where curved surfaces of thetool bit are of concave character greater than the arc of transversecurvature 90 of the grinding wheel. Flat or uniplanar edge surfaces suchas the surface 72 of the tool may be abraded by this method as therelative clearance afiorded by the curvature 90 of the grinding wheelresults in restricting the zone of abrasion to a narrow linear area.

It is to be understood that the phrases line contact and line engagementas used herein are relative in character as a grinding engagementnecessarily abrades material of the tool bit and, hence, the actual lineengagement obtains at the moment the template contour engages theabutment 80 to limit further abrasion or grinding. Thus when it isdesired, to shape, resharpen or reshape a form tool, the tool, bit mustnecesarily initially project a distance forwardly of the tool holder 68to insure that the tool engages the grinding wheel before the template75 engages the block 80. Hence, during the period that materialisbeingremoved bygrinding in azone-wherein the template 75 has not yetengaged the abutment 80, the grinding zone of contact with the tool willhave an appreciable width, but at no time is such zone more than a fewthousandths of an inch which is a relativelysmall grinding zone andwhich may be considered a line contact as compared with prior methods ofgrinding.

After the nose portions of the tool bit have been brought into grindingengagement with the wheel and the grinding in such several zonesapproaches completion because of the limiting factor of the template 75engaging the curved surface 81 of guide 80, the finish grinding of allpoints on the tool in elfect presents only a line engagement thereofwith the Wheel.

To eifectively utilize my apparatus for grinding to its fullestefficiency, the apparatus includes a means for presetting the tool bitin the holder 68 to accurately predetermine the extent of material to beremoved from the tool bit at one grinding operation. The grindingmachine is provided with a ball-shaped support 100. As illustrated inFigure 1, it is equipped with a hardened plate 101 in alignment with theposition of the tool 70 when the holder 68 is engaged with the ballsupport 100. The machine is provided with a micrometer arrangementincluding an adjustable member 103 whereby the template 75 engages themember 103, the latter being set or adjusted to a position indicatingthe extent that the tool bit 70, in contact with the indexing plate 101,projects forwardly of the template; and in this manner the amount ofmaterial to be removed from the tool bit 70, that is, the extent of thegrinding operation at a single setting of the tool, may be determined.An arrangement of this general character is disclosed and described indetail in Oliver Patent No. 2,552,645. However, by reason of thetransverse curvature of the grinding wheel periphery, the surface of themicrometer head 103 isa spherical section, the radius of which is thesame as that on the guide abutment 80. The transverse curvature of thesurface of plate 101 is the same as the transverse curavture of thegrinding wheel, i. e., having a radius one-half that of the curvedabtument surface of member 80.

The grinding machine illustrated is equipped with a template formingdevice which includes a ball-shaped tool holder support 105, a gauge orabutment block 107 and a supplemental grinding wheel 109, the latterbeing preferably of a cup-shaped configuration as illustrated inFigure 1. The grinding wheel 109 may be independently driven by anelectric motor 112 which is mounted upon a plate 114 slidably supportedupon horizontal ways 115 formed on the grinding machine frame 16. Theplate 114 supports a revoluble threaded member 116 cooperating with arelatively stationary nut 118, the threaded member being manipulated bymeans of a hand wheel 120 to adjust the relative position of thesupplemental grinding wheel 109.

In the use of the template forming device, a master form tool isinserted in the tool holder 68 in lieu of a tool bit blank and atemplate blank is secured to the upper end of the tool holder by meansof the clamping screw 76. The socket 71 of the tool holder is thenengaged with the ball support 105 and the template blank urged intoengagement with the supplemental grinding wheel 109 by manual pressureapplied to the tool holder by the operator. The grinding of the templatecontinues until all portions of the cutting contour of the master toolbit engages the abutment or gauge block 107. In this manner the templateis accurately ground to a contour double the size of the contour of themaster tool bit. The construction and details of template formation bythis method are disclosed in Oliver Patent No. 2,552,645.

Figure 12 is a diagrammatic view illustrating the relation of thetransversely curved periphery of the vwheel 27- and the curved guidesurface 81 of the abutment 80. As the holder 68 supports the tool bit orwork 70 midway between the center of the ball support 66 and the t m- 7plate- 75, the radius of curvature of the guide surface: 81 is twicethat of the transverse curvature of the grinding wheel 27;

The present invention is inclusive of an apparatus for shaping theperipheral grinding zone of the wheel 27 to a transverse arcuateconfiguration to carry out the grinding. As illustrated in Figure 7, awheel cutting or truing member 125 which is equipped with a diamondpoint 126 or the like for engagement with the wheel to be contoured issupported in a bore formed in a holder 127. .7

The wheel cutting or contouring tool 125 is adjustably held in theholder 127 by means of a threaded securing screw 129. The lowerextremity of the holderis formed with a socket 131 of semisphericalshape adapted to fit over the ball supports 66 and 100. By this mountingmeans the holder 127 is adapted for oscillatory movement about thecenter of curvature of the ball-shaped member 66 so that the diamondcutting tool 125 may be brought into engagement with the peripheral areaof the grinding wheel 27.

The upper extremity of the holder 127 is formed with a recess 133 withinwhich is mounted a pin 134 adapted for engagement with the curvedabutment or guide surface 81 to limit or determine the extent ofmovement 'of the truing diamond 126 toward the grinding wheel.

The pin 134 is preferably formed with an arcuate or curved zone 138. Thecurvature of the zone 138 is the same as that of the abutment blocksurface 81, and during the formation of transverse curvature on theperiphery of the grinding wheel 27 by means of the diamond truing device126, the engagement of the curved surface 138 of pin 134 with the curvedsurface 81 of the abutmnet 80 assures an arcuate guidance of the wheeltruing or cutting diamond 126 over the peripheral area of the grindingwheel. Wheel truing diamonds, because of their hardness, are processedunder conditions making it sometimes difficult to center the cuttingpoint of the diamond 126 with the longitudinal axi of the pin portion125. Thus by utilizing a curved surface on the pin 134 any error in thecentering of the diamond cutting point with respect to the axis of thepin portion would not affect the accuracy of the curvature formed on thegrinding wheel.

In the operation of the apparatus for contouring the periphery of thegrinding wheel 27, the holder 127 may be disposed upon the ball support100 and the pin 134 carried by the holder 127 engaged with themicrometer 103, which is initially set at index or zero position. Themicrometer head 103 may be adjusted forwardly the amount desired and thediamond point 126 of the memher 125 then brought into engagement withthe locating plate 101 and the screw 129 tightened upon the me. her 125to secure the latter in position in the holder 127. When the adjustmentof the wheel truing means has been effected in this manner, the socket131 of the holder 127 is engaged over the ball support 66 and thearcuate surface 138 of pin 134 urged toward the guide or abutment 81,thus bringing the wheel cutting diamond 126 into engagement with theperipheral surface of the grinding wheel 27. The operator oscillates theholder 127' around the center of the ball support 66 as an axis to movethe diamond 126 over the area. of the peripheral surface of the grindingwheel. The extent of movement of the truing diamond toward the wheel isdetermined by engagement of the curved surface 138 of pin 134 with thecurved guide surface 81. The operator continues to urge the holdertoward the guide 81 and oscillates the holder transversely over thearcuate path determined by the guide 81 until the diamond 126 hasimparted a curvature to the grinding wheel determined by the pattern ofcurvature of the guide 31.

The master template formed from a master tool by the supplementalgrinding wheel 169 is secured in the tool hodler 68 in the mannerhereinbefore pointed out. The holder 68 is then engaged with the ballsupport 160,

a formtool blank'IO or a form ool i whereha pened is fitted into theretaining block 83 inthe, manner shown in, Figure 3 and the forward edgeof the, template engagcd'. with the micrometer head 103. The. micrometermay be adinsted to a position determining the depth of material desiredto be, ground from the tool bit or blank which. is engaged with theabutment or indexing plate 101, the tool bitor blank being then securedto the holder 68 by manipulation of the locking cam 85 through themedium of the screw 87. The holder 68 carrying the form tool bit orblank and the template is then disposed with the socket 71 of the toolholder engaging the ball support 66. The operator then manually urgesthe holder toward the grinding wheel with the template aligned forultimate engagement with the guide or abutment 80, which action bringsthe cutting end zone of the form tool blank or bit into engagement withthe grinding wheel.

Due to the transverse curvature of the periphery of the grinding wheel,only a very narrow, substantially vertical band or zone of the tool bitor blank engages the wheel 27 so that grinding or abrasion takes placeat a rapid rate. The operatorcontinues the grinding operation,oscillating the holder 68 about the center of the ball support as anaxis until all portions of the pattern of the template have been engagedwith the abutment guide surface 81, and at the finish grinding, that is,at the point where the template engages the abutment, the grinding areaof the tool engaging the grinding wheel is a substantially line contact.Thus, by this grinding apparatus, the removal of material by abrasion isvery rapid because of the limited area of abrasion taking placeat anyparticular moment. Thus, hardened tools, such as tungsten carbide, maybe successfully abraded and formed to predetermined desiredconfiguration through theuse of the apparatus herein shown anddescribed.-

It is apparent that, within the scope of the invention, modificationsand different arrangements may be made other than is herein disclosed,and the present disclosure is illustrative merely, the inventioncomprehending all variations thereof.

What I claim is:

1. Apparatus for grinding form tools in combination with a grindingmachine having a frame supporting a rotatable grinding wheel formed witha transversely curved grinding zone and a spherically shaped mountingelement for a tool carrying holder, means for adjusting the holdermounting element relative to the grinding wheel in a, directionsubstantially tangential of the periphery of the wheel, a formtool-carrying holder having one end supported upon the mounting elementfor oscillatory movement about the center of said spherically shapedelement, the opposite end of the holder carrying a template shaped tothe configuration to be imparted to the form tool by engagement with thegrinding wheel, said holder being formed with means intermediate itsends for supporting a form tool to be ground, an abutment member havinga curved surface of a radius substantially larger than that of thetransverse curvature of the peripheral grinding zone of said grindingwheel arranged to be engaged by the template, the curved surface of saidabutment member and the curved grinding zone of said grinding wheel atthe point of contact with said tool having the planes of their arcs ofcurvature in spaced parallel relation with one another and their arcs ofcurvature located on the surface of a cone vertically generated from thecenter of said spherically-shaped mounting element, whereby grinding ofthe form tool is effected through a comparatively narrow linear zonetangentially of the periphery of the grinding wheel.

2. Apparatus for grinding form tools as in claim 1, and wherein theradius of the curved surface of said abutment member is substantiallytwice that of the transverse curvature of the peripheral grinding zoneof said grinding 1,522,109 wheel. 2,279,092 2,391,122 References Citedin the file of this patent 2,552,645

UNITED STATES PATENTS 5 1,233,608 Sacrey July 17, 1917 10 Fiddyment Jan.6, 1925 Olson Apr. 7, 1942 Bunker et a1. Dec. 18, 1945 Oliver May 15,1951

